Question

For affine cipher, the key is a = 17, b = 10 so the enciphering function...

For affine cipher, the key is a = 17, b = 10 so the enciphering function is

C(7,10)(p) = 17p + 10 mod 26.

a) Find the deciphering function for this cipher. Show your steps

b) If the ciphertext is AKV, what is the plaintext?

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Homework Answers

Answer #1

a) Let denote plane text and denote cipher text.

Given the enciphering function

That is

Which implies

We have for any integer coprime to 26

Since 17 is coprime to 26, from above we get

Now

Then

b)

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